Cement manufacturing releases CO2 into the atmosphere both directly when calcium carbonate is heated, producing lime and carbon dioxide, and also indirectly through the use of energy if its production involves the emission of CO2. The cement industry is the second largest CO2 emitting industry behind power generation. The cement industry produces about 5% of global man-made CO2 emissions, of which 60% is from the chemical process, and 40% from burning fuel. The amount of CO2 emitted by the cement industry is nearly 900 kg of CO2 for every 1000 kg of cement produced.
Amine or ammonia based absorption processes, such as the monoethanolamine (MEA) based process, is considered to be a viable technology for capturing CO2 from low-pressure exhaust gas streams, e.g. in cement manufacturing plants. CO2 in the gas stream is captured in the liquid absorbent solution in an absorption process. A CO2 absorber is employed to establish suitable conditions (temperature, pressure, turbulence, etc.) for chemical absorption of CO2 from a mixed gas stream into the liquid absorbent.
The liquid absorbent containing absorbed CO2 is subsequently regenerated, whereby absorbed CO2 is separated from the absorbent, and the regenerated absorbent is then reused in the CO2 absorption process. Thus, a circulating absorbent stream is formed. Regeneration is generally achieved by heating the liquid absorbent in a regenerator to a temperature at which CO2 is released from the absorbent.
Regeneration of the liquid absorbent, for example using a stripper reboiler, is generally an energy intensive process. Accordingly, there is a need for processes that improve and optimize the utilization of energy in such systems.